1. Field of the Invention
The present invention relates to a train detection system.
2. Description of Related Art
Train detection systems of this nature have been known under the designation "axle counters" for some time. A detailed description thereof is contained in "Signal+Draht", Vol. 59 (1967), No. 11, pages 165 to 174. They work on the simple principle that a section of track defined by detection points is only indicated as being unoccupied if the number of axles having entered the section is equal to the number of axles having left the section. In order to be able to determine this, it is necessary to identify both the number and direction of travel of the axles passing a detection point at all direction points that define the section of track to be indicated as being unoccupied or occupied. In order to accomplish this in known systems, the signals from the axle detectors are first amplified and then provided to an evaluation unit, the so-called axle-counting group, via separate multiple-conductor cables. The number of axles and their direction of travel are determined in the evaluation unit.
The prior-art system is very expensive, primarily as a result of the fact that each section of track requires a separate evaluation unit and, if the section of track is defined by more than two detection points, requires further supplementary groups. Moreover, many cable links are required, as it is necessary for each detection point to be connected separately to the evaluation unit.
Further disadvantages of the prior-art train detection system operating in accordance with the axle-counting principle are the interference susceptibility of the transmission link between the detection points and the evaluation unit in the interlocking and the fact that it is not possible to check the components located in the outdoor equipment from the central evaluation unit.